1. Field of the Invention
The present invention relates to a method and apparatus for transmitting an electrical pulse in body tissue, and in particular, the present invention relates to a method and apparatus for transmitting an electrical signal between an electrode positioned on a housing of an implantable medical device and electrodes positioned along a lead body of the device.
2. Description of the Related Art
Since the introduction of the first implantable pacemakers in the 1960s, there have been considerable advancements in both the fields of electronics and medicine, leading to a wide assortment of commercially available implantable medical devices. These implantable medical devices include therapeutic and diagnostic devices, such as pacemakers, cardioverters, defibrillators, neural stimulators, and drug administering devices, among others. Today's state-of-the-art implantable medical devices are vastly more sophisticated and complex than their early counterparts, and are capable of performing significantly more complex tasks and providing increased therapeutic benefits.
Such implantable medical devices generally include a control unit, implanted within the patient's body, that is capable of delivering electrical signals to or receiving electrical signals from one or more leads extending from the control unit to an area of the body being treated, for example, the heart, a nerve bundle, or the like. The control unit is generally housed within a biologically inert, electrically conductive can. In certain cases, the can may be used as an electrode itself. For example, electrical signals (e.g., pacing signals, neural stimulation signals, defibrillating pulses, and the like) emitted from one or more lead electrodes may be received by the can after traveling through the body. Depending upon the type and magnitude of the signal, muscle tissue in close proximity to the electrically conductive can may be stimulated as a result of the electrical interface effects between the can and the surrounding muscle tissue.
Further, it may be desirable in certain cases to transmit a pacing, stimulation, or defibrillation signal or signals through tissue between two electrodes disposed along the lead. However, in certain situations it may not be possible to ensure with absolute certainty that both electrodes will be in adequate electrical contact with the tissue. Thus, in such situations the signal or signals may not be successful in affecting the tissue as desired.